Method for purifying N-(alpha-alkoxyethyl)formamide, method for producing high-purity N-(alpha-alkoxyethyl)formamide, and device for purifying N-(alpha-alkoxyethyl)formamide

Abstract

A method for purifying an N-(α-alkoxyethyl)formamide contained in a mixture thereof with a plurality of distillation columns, the plurality of distillation columns being arranged serially, the method including condensing a distillate from the second or any later-stage distillation column to obtain a condensate and returning at least some of the condensate to the preceding distillation column.

The invention claimed is: 
     
       1. A method for purifying N-(α-alkoxyethyl)formamide from a mixture containing the N-(α-alkoxyethyl)formamide by using a plurality of distillation columns, wherein
 the plurality of distillation columns are disposed in series, and 
 the method comprises: 
 introducing a column bottom liquid of one of the distillation columns into a distillation column at a subsequent stage; 
 condensing an overhead efflux of the distillation column at a subsequent stage to obtain a condensate; and 
 returning at least a part of the condensate to a distillation column at a preceding stage. 
 
     
     
       2. The method for purifying N-(α-alkoxyethyl)formamide according to  claim 1 , wherein the condensation is conducted by using a condenser. 
     
     
       3. The method for purifying N-(α-alkoxyethyl)formamide according to  claim 1 , wherein at least one of the plurality of distillation columns is a packed column. 
     
     
       4. The method for purifying N-(α-alkoxyethyl)formamide according to  claim 1 , wherein a temperature of a column bottom liquid in at least one distillation column among the plurality of distillation columns is 100° C. or less. 
     
     
       5. The method for purifying N-(α-alkoxyethyl)formamide according to  claim 1 , wherein the mixture contains water and an alcohol. 
     
     
       6. The method for purifying N-(α-alkoxyethyl)formamide according to  claim 1 , wherein the condensate contains water and N-(α-alkoxyethyl)formamide. 
     
     
       7. A method for producing high-purity N-(α-alkoxyethyl)formamide from a mixture containing the N-(α-alkoxyethyl)formamide, water, and an alcohol by using a plurality of distillation columns, wherein
 the plurality of distillation columns are disposed in series, and 
 the method comprises: 
 obtaining an overhead efflux containing an alcohol at a preceding stage and a column bottom liquid at a preceding stage in a distillation column at a preceding stage; 
 introducing the column bottom liquid at a preceding stage into a distillation column at a subsequent stage; 
 obtaining an overhead efflux containing water and N-(α-alkoxyethyl)formamide at a subsequent stage and a column bottom liquid containing N-(α-alkoxyethyl)formamide at a subsequent stage in the distillation column at a subsequent stage; 
 condensing the overhead efflux at a subsequent stage to obtain a condensate; and 
 returning at least a part of the condensate to the distillation column at a preceding stage. 
 
     
     
       8. A device for purifying N-(α-alkoxyethyl)formamide, comprising a plurality of distillation columns for distilling N-(α-alkoxyethyl)formamide-containing liquid, wherein
 the plurality of distillation columns are disposed in series such that a column bottom liquid of one of the distillation columns is introduced into a distillation column at a subsequent stage, and 
 the device comprises a return section for returning at least a part of a condensate of an overhead efflux of the distillation column at a subsequent stage to a distillation column at a preceding stage. 
 
     
     
       9. The device for purifying N-(α-alkoxyethyl)formamide according to  claim 8 , comprising a condenser for condensing the overhead efflux of the distillation column at a subsequent stage. 
     
     
       10. The device for purifying N-(α-alkoxyethyl)formamide according to  claim 9 , wherein the condenser is connected to a column top of the distillation column. 
     
     
       11. The device for purifying N-(α-alkoxyethyl)formamide according to  claim 8 , wherein at least one of the plurality of distillation columns is a packed column.